HotMelt adhesives are typically made of a high molecular weight polymer, a tackifier, a wax and a plastizicer formulated so as to display a glass transition temperature below the lowest service temperature and a suitably high melt temperature. Typical high molecular weight polymers used are high molecular weight polyolefins such as polyethylene, polyamides, polyesters synthetized from a diol and a dicarboxylic acid, copolymers of an unsaturated aliphatic hydrocarbon and an acrylate ester or acid (e.g. Ethylene-acrylate copolymer, ethylene-acrylate-maleic anhydride terpolymers, ethylene n-butyl acrylate (EBA), ethylene-acrylic acid (EAA) or ethylene-ethyl acetate (EEA)), polyurethanes such as thermoplastic polyurethanes or reactive polyurethanes, copolymers of an unsaturated aliphatic hydrocarbon and a vinyl aliphatic ester (e.g. Ethylene-vinyl acetate (EVA) copolymers) or styrene block co-polymers. The most widely used tackifiers are resins such as rosin resin or terpenes. HotMelt adhesives are applied hot over the adhered typically by use of an electric hot glue gun, but also through spraying or dipping. Upon cooling, the adhesive marries the adhered. Some of the compounds mentioned in the literature as plasticizers are glycerol, ethylene glycol, propylene glycol or polyether polyols (see for example, US 2014/163149—Avery Dennison Corp., or EP 2 499 194 B1—Adhesives Research). PSA adhesives represent a broader kind of adhesives which marry the adhered by application of pressure. PSA can be made of an elastomer and a tackifier, some of which are also used in HotMelt compositions. Typical elastomers used are vinyl ethers, copolymers of an acrylate esters or acids (e.g. Ethylene-acrylate copolymer, ethylene-acrylate-maleic anhydride terpolymers, ethylene n-butyl acrylate (EBA), ethylene-acrylic acid (EAA) or ethylene-ethyl acetate (EEA)), nitriles, copolymers of an unsaturated aliphatic hydrocarbon and a vinyl aliphatic ester (e.g. Ethylene-vinyl acetate (EVA) copolymers) or styrene block co-polymers. The most widely used tackifiers are also resins such as rosin resin. Exemplary compositions of traditional HotMelt or PSA compositions are disclosed in many patents such as U.S. Pat. No. 4,602,056 (Bayer) or US 2012/213992 (BASF), respectively.
Some documents also mention the possibility of incorporating polyalkylenecarbonates (PAC), such as polypropylenecarbonate (e.g. Eternacoll® of UBE or Duranol of Asahi), also known as polyol polycarbonates (e.g. US 2005/137275), and which are polymers resulting from the reaction of diols like 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol or thiodiglycol, with organic carbonates, for example diphenyl carbonate or dimethyl carbonate, or with phosgene (see for example (U.S. Pat. No. 5,872,183)), and are thus polycarbonates with essentially 100% carbonate links:HOR—O—C(═O)—OnR—OH
For example, EP 1 527 146 B1 (Cytec Surface Specialties, S.A.) discloses a PSA adhesive comprising a. an acrylate copolymer; b. at least a polyol selected from the group consisting of polyester polyols, acrylic polyols, polycarbonate polyols and polyether polyols; and c. at least one transition metal complex as cross-linking agent. No further information is given about the polycarbonate polyols mentioned, and all examples refer to polyether polyols. All the above have drawbacks, such as the need to use large amounts of resins or the need to use of crosslinkers.
In the same way, U.S. Pat. No. 6,468,650 discloses a mixture of specific EVA co-polymers and polyether polyols which can be capped with terminal groups. Concretely, the polyether polyol can be of formula XO—[(CH2)4—O]—Y (1) or of XO—[(CH(CH3)—CH2—O]—Y (2), wherein, X and Y are selected from the group consisting of H—, (CnH2n+1)— where n is from 1 to 20, CH2—CHCO—, CH3CH(NH2)CH2—, 2,3-epoxypropyl, C6H5—CO—, and CH2—C(CH3)—CO—. All examples make use of polyether polyols.
On the other hand, polymers which can improve the carbon footprint of industrial processes have drawn considerable attention in response to increasing environmental awareness and stricter regulation. One family of these polymers are carbonate polyols, which are the result of the reaction between an epoxide and CO2, and thus help in capturing carbon dioxide. In these polymers the epoxide and CO2 can completely alternate so as to provide copolymers which backbone essentially comprise carbonate linkages, that is a polymer similar to PACs (or polyol polycarbonates) or, on the other hand, provide copolymers wherein the epoxide and CO2 can form blocks resulting in a backbone which has, both, carbonate and ether links, that is, were the carbon dioxide is randomly inserted between blocks of polyether (known as polyether carbonate polyols).
Totally alternate, i.e. polycarbonate polyols, are described for example in WO 2011/163250 and WO 2013/158621A (Novomer), and are prepared using Co-Salen type catalysts. These polymers thus have a similar backbone to those polycarbonates shown in the above formula, made with essentially 100% carbonate links. Such polycarbonate polyols are then used to produce polyurethanes.
Adhesives made of aliphatic polycarbonates are disclosed in WO 2010/060038 (Novomer), also prepared using Co-Salen type catalysts, and which have a carbonate linkage above 85%; according to the authors carbonate linkages below 90% are not suitable for adhesives. Further polyether carbonate polyols are disclosed in the co-pending application EP15382178.0 or in EP 2 837 648 (REPSOL), which are prepared by co-polymerization of an epoxide and CO2 in the presence of a double metal cyanide (DMC) catalyst, and on the contrary present low carbonate linkage percentage; said polyether carbonate polyols are used for the preparation of polyurethanes.